RUI: Fronts and Patterns in Advection-Reaction-Diffusion Systems

Thomas H. Solomon, Bucknell University, DMR 0703635

We are conducting experiments to study how vortices (swirling flows) affect the motion of reaction fronts, such as forest fires or spreading diseases. During the past year, we have found:

• Reaction fronts tend to ”lock” to vortex patterns, resulting in “faceted” fronts, similar to smooth, faceted crystal patterns in growing solids.

• Moving vortices grab and “pin” reaction fronts. We expect this result to form the basis for a general theory of the effects of vortices on fronts both simple and complicated flows.

Refs: Phys. Rev. Lett. 100, 028302 (2008);Europhys. Lett., in press (2008).

Reaction front “locking” to osci-llating array of

vortices.

Pair of spirals acting as a generator for a continuing pattern of

fronts

Reaction front pinned to a random vortex pattern moving upward through a flow. (The movie

follows the vortices.)

Societal Impact:Fluid mixing (advection) is significant in a wide range of reacting systems with significant societal impact. Some examples include: (a) chemical and biological processes, particularly in microfluidic devices; (b) plasmas, e.g., in fusion reactors; (c) developing embryos where flow-induced pattern formation may play a role in segregation of different parts of an embryo into specialized functions; and (d) storm and pressure fronts in the atmosphere. It is also possible that modeling of a moving population as a fluid might shed insight into spreading of diseases in society.

Education:During the past year, four undergraduate students (Mollie Schwartz, Jeff Boehmer, Garrett O’Malley and Justin Winokur) contributed to this project. The students also interacted with REU students working in the Department of Physics & Astronomy at Bucknell. Two of these students are already first authors on refereed journals and have given talks at international conferences. The PI has also participated in outreach activities to local high schools.

RUI: Fronts and Patterns in Advection-Reaction-Diffusion Systems

Thomas H. Solomon, Bucknell University, DMR 0703635

Participants in Bucknell’s 2008

Summer Undergraduate

Research Program in Physics & Astronomy